Inductive storage ignition system

ABSTRACT

An inductive storage ignition system for an internal combustion engine includes a pair of silicon controlled rectifiers (SCR&#39;&#39;s) between the anodes of which is connected a commutating capacitor. The anode of a first one of the SCR&#39;&#39;s is connected to the vehicle ignition coil which in turn is connected to the positive terminal of the vehicle battery. The anode of the other SCR is connected to a direct current high voltage source. The gate electrodes of the SCR&#39;&#39;s are connected to the ignition points of the vehicle for alternate operation thereby. The high voltage source charges the commutating capacitor which supplies a reverse direct current high voltage pulse at the anode of the first SCR upon operation of the second SCR to conduction by the points, to ensure turn off of the first SCR despite any forward voltage transients produced at the ignition coil.

United States Patent 1191 Gunderson et al.

1111 3, 32,987 Sept. 3, 1974 1 INDUCTIVE STORAGE IGNITION SYSTEM Primary Examiner-Laurence M. Goodridge ld B. Cox [75] Inventors. Philip D. Gunderson Pros ect Exammer R Y Heights; Chi Sun Lai Lalge Zurich, Attorney, Agent, or Firm-Donald J. Lisa; Vincent J. both of 111.

[73] Assignee: Motorola, Inc., Franklin Park, Ill. [57] ABSTRACT [22] Filed: 1973 An inductive storage ignition system for an internal [21] APPL No: 337,615 cornbustion engine includes a pair of silicon controlled rectifiers (SCRs) between the anodes of which 1s connected a commutating capacitor. The anode of a first [52] US. Cl 123/148 E, 123/148 R one of the SCRs is connected to the vehicle i i [51 Illt. Cl. 6 in turn is to the [58] Field of Search 123/148 E; 315/242, 223 f h vehicle battery. The anode of the other SCR is connected to a direct current high voltage source. The [56] References C'ted I gate electrodes of the SCRs are connected to the igni- UNITED STATES PATENTS tion points of the vehicle for alternate operation 3,260,251 7/1966 Lange 123/148 E y- The high Voltage Source Charges the commu- 3,331,362 7/1967 Mitchell 123/148 E tating capacitor which supplies a reverse direct cur- 3,424,944 1/1969 Nilssen 123/148 E rent high voltage pulse at the anode of the first SCR 8,580 11/1971 Dogadko..... 123/148 E upon operation of the second SCR to conduction by 3,635,202 1/ 123/148 E the points, to ensure turn off of the first SCR despite 3,665,908 5/1972 OIShl 123/148 E I y forward o g transients produced at the g ig tion coil.

4 Claims, 2 Drawing Figures /2 BATLERY To 1 /4 I? r 40 ms'rm u-ro v4. HIGH VOLTAGE [2b 2a POWER 27 I SUPPLY l6 Ill 25 INVERTER 2 7 J PAIENTED 31974 3,832,987

/2 BAT'LERY l4 /7 I5 40 DISTRTIBUTOR 1 a Ty HIGH VOLTAGE POWER 2:: H /20 27 I SUPPLY ,6 I d :\d-36 /& 22 32: 44 48 28 26 Agra-:3 f

TO DISTRIBUTOR INDUCTIVE STORAGE IGNITION SYSTEM BACKGROUND DESCRIPTION OF THE DRAWING In the drawing:

FIG. 1 is a simplified schematic diagram of an SCR,

This invention relates generally to electronic ignition 5 inductive storage ignition system according to the insystems for internal combustion engines and more particularly to silicon controlled rectifier inductive storage ignition systems.

Inductive storage ignition systems which use a pair of silicon controlled rectifiers (SCRs) and a commutation capacitor are known in the art. Typically, in these systems, the ignition coil is coupled between the positive terminal of the vehicle battery and the junction of the anode of one of the SCRs and one side of the commutating capacitor, and the junction of the anode of the other SCR and the other side of the capacitor is coupled through a resistor to the battery as well. A circuit interrupter, such as ignition points, connected to the gate electrodes of the SCRs alternately renders them conductive. When the SCR coupled to the ignition coil is to be turned off, the heavy current through the ignition coil produces a high forward voltage transient at the anode of the SCR which tends to maintain the last-mentioned component on. When this occurs, the operation of the ignition system is disrupted.

It has been attempted to overcome this by the provision of a larger commutating capacitor in the system to slow down the rise time of the transient to prevent the latter from affecting the turn off of the SCR. While this method produces some good results, the large capacitor reduces the voltage available to the spark plugs of the internal combustion engine in which the ignition system is employed.

SUMMARY 3 Accordingly, it is a primary object of the present invention to provide a new and improved SCR inductive storage ignition system which overcomes the drawbacks of prior art systems.

It is another object of the present invention to provide a new and improved SCR inductive storage ignition system which is relatively simple to fabricate and is efficient in operation.

Briefly, a preferred embodiment of an SCR inductive storage ignition system according to the invention includes a pair of silicon controlled rectifiers between the anodes of which is connected at commutating capacitor. The anode of a first one of the SCR's is connected through the vehicle ignition coil to the positive side of the vehicle battery, and the anode of the other SCR is connected through a low current, high voltage power supply, also to the positive side of the battery. The gates of the SCRs are coupled to the ignition points of the vehicle in which the system is used, with an electronic inverter circuit being interposed between the gate electrode of the first-mentioned SCR and the ignition points to provide out of phase pulses from the points In operation, the low current, high voltage power supply ensures turn off of the first-mentioned SCR regardless of the inductive voltage kick produced atthe anode of the SCR when attempting to turn it off. The high voltage, on' the order of 150-200 DC volts, from the supply, ensures a positive turn off of the SCR despite any forward voltage transients produced at the ignition coil.

-vention; and

FIG. 2 is a more detailed schematic diagram of a pre ferred embodiment of the ignition system of FIG. 1.

DETAILED DESCRIPTION Referring now to the drawing wherein like numerals have been used throughout the various views to indicate similar components, there is illustrated in FIG. 1, a simple schematic diagram of an SCR inductive storage ignition system 10 according to the invention.

The ignition system 10 includes an ignition coil indicated by the numeral 12, having primary and secondary windings 12a, 12b, respectively. The coil is connected at one side thereof via lead 14 and a ballast resistor 17, to the positive terminal 15 of a vehicle storage battery. The opposite side of the coil 12 is connected at junction 16 to the anode 18 of a first silicon controlled rectifier (SCR) 20 and via lead 22, to one side of a commutating capacitor 24. The cathode 26 of SCR 20 is connected to ground potential.

A second SCR 28 is connected at the anode 30 thereof to the junction 32, whereat, through lead 34, the other side of the commutating capacitor 24 is also connected along with the output side of a low current, high voltage power supply 38. The input to the lastmentioned power supply is connected via lead 40 to the positive tenninal 15 of the vehicle battery. The cathode 42 of SCR 28 is connected to ground potential.

The gate electrodes 44, 46, of the SCRs 20, 28, respectively, are coupled at junction 48 to one side of the ignition points 50 of the ignition system. While conventional ignition points are shown and described, other suitable circuit interrupting devices or means for providing control pulses of the well known type, may be vehicle, SCR 20 is rendered conductive to pass current from the vehicle battery through the ignition coil 12 to ground. During this time, the commutating capacitor 24 is charged from the high voltage power supply through SCR 20 to ground. The capacitor is charged with the polarity shown in FIG. 1 of the drawing to approximately l50-200 DC volts.

When points 50 are opened to produce an ignition pulse in the secondary 12b and coil 12, a gate signal is applied to gate 46 of SCR 28 to render it conductive. The voltage potential at the anode of the lastmentioned SCR drops to ground, to in turn drop the positive polarity side of capacitor 24 to ground potential, placing a negative -200 DC volts on the anode of SCR 20. With the negative high voltage potential ap voltage transient produced incoil 12 due to the turn off of SCR which may tend to keep SCR 20 in a conductive state, is overcome by the negative high voltage which turns the SCR ofi.

Upon turning SCR 20 off and while SCR 28 is conducting, the commutating capacitor 24 is charged by the vehicle battery through coil 12 and SCR 28 in a direction opposite from that shown in the drawing. Upon the closing of points 50 once again, a pulse is applied to gate 44 of SCR 20, through the inverter cricuit to provide a positive pulse, which turns SCR 20 on or renders it conductive. Turning SCR 20 on brings anode 18 thereof to ground potential, applying the negative battery voltage stored in capacitor 24 at the anode of SCR 28 to turn it off. Only the negative voltage supplied from the battery, i.e. approximately twelve volts, is required to turn SCR 28 off. No inductive transient is produced thereat as in the case with SCR 20, since the high voltage power supply is of a low current type, and as such produces no large voltage transient at junction 32 upon turning off SCR 28.

The operation of the circuit continues as described above for successive openings and closings of points 50.

Referring now to FIG. 2 of the drawing, there is shown therein a preferred embodiment 60 of the SCR inductive storage ignition system according to the invention.

In the embodiment 60 of the SCR inductive storage ignition system, the high voltage power supply is shown in dashed box 38 as including an oscillator circuit 62 including a transistor 64. The oscillator circuit produces an alternating current output in primary winding 66 of the step-up transformer 68 to induce a voltage in secondary 70, which is rectified by diode 72 and filtered by capacitor 74, and thereafter applied at junction 32 at the anode of SCR 28. The DC voltage produced is as described heretofore, approximately 150-200 volts.

A non-inverting amplifier circuit shown in dashed box 76, is provided between gate 46 and junction 48. The circuit provides an amplified signal from points 50 to gate SCR 28 on as described heretofore. The noninverting amplifier circuit operates as follows: when points 50 are opened, the transistor 78 of the circuit is turned on by the current through resistor 27 connected between the battery and junction 48 (on one side of points 50). Thereafter, upon the closing of the points, the current is shunted to ground through the points and transistor 78 is thus turned off. The capacitor 80 and diode 82 of the circuit serve as a pulse shaper. When the transistor 78 is on, the voltage drop at the collector 84 thereof, through diode 82, turns ofi transistor 86. The voltage at the collector 88 of transistor 86 then becomes sufficient to gate the SCR 28 on. Upon charging capacitor 80 to a fully charged state, the current flow therethrough is stopped and transistor 86 is turned on through resistor 89. SCR 28 remains on until turned off by the application at junction 32 of a high reverse volta e.

The inverter circuit shown in dashed block 52 of the drawing, is an inverting amplifier circuit, and operates essentially like the non-inverting amplifier circuit 76, except the operation thereof to gate on SCR 20 is 180 out of phase with the operation of the non-inverting amplifier circuit 76. In operation, the transistor 90 operates like transistor 86 of circuit 76 and diode 92, capacitor 94 and resistor 96 provide the same function as diode 82, capacitor and resistor 89, respectively, of the circuit 76.

The ignition coil 12 in the circuit embodiment 60 is shown as including a primary 98 and secondary 100, the latter of which is connected to the distributor for distribution of the spark to the various spark plugs of the internal combustion engine with which the ignition circuit is employed.

While a particular embodiment of the invention has been shown and described, it should be understood that the invention is not limited thereto since many modifications may be made. It is therefore contemplated to cover by the present application any and all such modifications as fall within the true spirit and scope of the appended claims.

We claim:

1. In an inductive storage ignition system for internal combustion engines including ignition coil means and a source of direct current voltage, in combination: first and second controllable semi-conductor rectifier means each having first and second electrodes, the first electrode of said first controllable semi-conductor rectifier means being connected in series relation with said ignition coil means, means coupling said ignition coil means to said direct current voltage source, a high voltage direct current voltage source connected in series with the first electrode of said second controllable semi-conductor rectifier means, pulse producing means operated by the engine in synchronism therewith and co-operating with both said controllable semiconductor rectifier means for alternately rendering one of said rectifier means conductive, commutating capacitor means connected between the first electrodes of said controllable semi-conductor rectifier means, said capacitor means being charged in a first polarity by said direct current high voltage source in response to the operation of said first controllable semi-conductor rectifier means to a conductive state, and being discharged to supply a reverse polarity direct current high voltage at the first electrode of said first controllable semiconductor rectifier means upon said second controllable semi-conductor rectifier means being rendered conductive to operate said first controllable semiconductor rectifier means to a non-conductive state despite any voltage transients of said first polarity produced in said ignition coil.

2. An inductive storage ignition system as claimed in claim 1 wherein said high voltage source includes oscillator means for producing a relatively low alternating current voltage, voltage step-up means for converting said relatively low alternating current voltage into a relatively high alternating current voltage and rectifier means for rectifying said relatively high alternating current voltage to produce a relatively high direct current voltage for charging said commutating capacitor.

3. An inductive storage ignition system as claimed in claim 1 wherein each of said controllable semiconductor rectifier means includes a control electrode, each of said control electrodes being coupled electrically to said pulse producing means, and wherein said system further includes pulse inverting circuit means interposed electrically between said pulse producing means and the control electrode of one of said rectifier means for providing control pulses thereto l80 out of phase with respect to pulses provided to said other control electrode for rendering said first and second conwherein the input electrode of said first silicon controlled rectifier is connected in series relation with said ignition coil, wherein said high voltage source is connected to the input electrode of said second silicon controlled rectifier and wherein said commutating capacitor is connected between said input electrodes of said first and second silicon controlled rectifiers. 

1. In an inductive storage ignition system for internal combustion engines including ignition coil means and a source of direct current voltage, in combination: first and second controllable semi-conductor rectifier means each having first and second electrodes, the first electrode of said first controllable semi-conductor rectifier means being connected in series relation with said ignition coil means, means coupling said ignition coil means to said direct current voltage source, a high voltage direct current voltage source connected in series with the first electrode of said second controllable semi-conductor rectifier means, pulse producing means operated by the engine in synchronism therewith and co-operating with both said controllable semi-conductor rectifier means for alternately rendering one of said rectifier means conductive, commutating capacitor means connected between the first electrodes of said controllable semi-conductor rectifier means, said capacitor means being charged in a first polarity by said direct current high voltage source in response to the operation of said first controllable semi-conductor rectifier means to a conductive state, and being discharged to supply a reverse polarity direct current high voltage at the first electrode of said first controllable semi-conductor rectifier means upon said second controllable semi-conductor rectifier means being rendered conductive to operate said first controllable semi-conductor rectifier means to a non-conductive state despite any voltage transients of said first polarity produced in said ignition coil.
 2. An inductive storage ignition system as claimed in claim 1 wherein said high voltage source includes oscillator means for producing a relatively low alternating current voltage, voltage step-up means for converting said relatively low alternating current voltage into a relatively high alternating current voltage and rectifier means for rectifying said relatively high alternating current voltage to produce a relatively high direct current voltage for charging said commutating capacitor.
 3. An inductive storage ignition system as claimed in claim 1 wherein each of said controllable semi-conductor rectifier means includes a control electrode, each of said control electrodes being coupled electrically to said pulse producing means, and wherein said system further includes pulse inverting circuit means interposed electrically between said pulse producing means and the control electrode of one of said rectifier means for providing control pulses thereto 180* out of phase with respect to pulses provided to said other control electrode for rendering said first and second controllable semi-conductor rectifier means conductive alternately.
 4. An inductive storage ignition system as claimed in claim 3 wherein each of said controllable semi-conductor rectifier means includes a silicon controlled rectifier having an input, output and control electrode, wherein the output electrodes of said silicon control rectifiers are connected to a reference potential and wherein the input electrode of said first silicon controlled rectifier is connected in series relation with said ignition coil, wherein said high voltage source is connected to the input electrode of said second silicon controlled rectifier and wherein said commutating capacitor is connected between said input electrodes of said first and second silicon controlled rectifiers. 